Cleaning compositions in gel form have utility for many household, industrial, and institutional applications. In most instances, such gels have “soft” and readily flowable rheological properties. In these instances, the cleaning products are generally dispensed from containers or devices and do not involve direct handling/physical manipulation of the cleaner formulation by the user. For some cleaning applications, however, handling/manipulation of the cleaner formulation may be highly desirable. The placement/adhesion of a unit dose of gel cleaner onto a toilet bowl, urinal, or shower wall surface, where the gel is intended to reside for an extended period of time, being slowly eroded/dissolved over time via repeated flushing with water, may be desirable. Self-adhering aqueous cleaning gel compositions are known for use as continuous hard surface cleaning systems, such as for flush toilets, wherein water passes over the gel with each flush of the toilet, thereby eroding or dissolving a minor amount of the composition with each flush and distributing cleaning ingredients to the toilet water and toilet bowl surface above and/or below the water line depending on the components of the gel. Other examples include placing a unit dose of gel cleaner into a designated dispensing chamber, such as a toilet bowl rimblock holder or the cleaner-dispensing cavity of an automatic dishwasher.
In cleaning applications such as these, it may be desirable to employ a rigid, “hard” aqueous gel that resists deformation of intended shape and that can be easily manufactured and subsequently handled by the end-user. It may also be desirable that unit doses of these gels retain their shape after manufacturing, up to and including when said gel products are handled by the end-user. To meet this requirement, such gels should desirably be resistant to heat-induced shape changes as packaged and stored after manufacturing, up to the end-use occasion. This includes storage of such products at reasonably anticipated elevated temperatures, such as a hot warehouse, shipping container, or end-use location. Since water is a major component of the gels, it is desirable that the gels are capable of being processed/manufactured at ambient atmospheric pressure and temperatures well below the boiling point of water.